Frequency hopping interference detection using decoder codeword metrics

Abstract

A method for mitigating interference in a frequency hopping channel system based on codeword metrics obtained during decoding of codewords. The method includes decoding a plurality of codewords using a particular error control coding method. Each of the plurality of codewords includes portions received from plurality of channels in the frequency hopping channel system. For each decoded codeword, one or more codeword metrics are obtained based on the cost of correcting errors during decoding of the plurality of codewords. Based on the codeword metrics, one or more channel metrics are inferred. Based on the inferred one or more channel metrics, a reliability metric of a particular channel is reduced, or incoming symbols received from the particular channel are ignored during decoding.

What is claimed is: 
     
       1. A method for mitigating interference in a frequency hopping channel system based on codeword metrics obtained during decoding of code blocks, the method comprising:
 decoding a plurality of code blocks into a plurality of codewords using a particular error control coding method, each of the plurality of code blocks comprising portions received from a plurality of channels in the frequency hopping channel system; 
 for each decoded code block, determining one or more codeword metrics based on cost of correcting errors during decoding of the plurality of code blocks; 
 inferring one or more channel metrics of the plurality of channels based on the one or more codeword metrics of the plurality of codewords; and 
 based on the channel metrics, reducing a reliability metric of a particular channel or ignoring incoming symbols received via a particular channel during decoding of code blocks. 
 
     
     
       2. The method of  claim 1 , wherein the one or more codeword metrics include a number of errors corrected during decoding of a code block. 
     
     
       3. The method of  claim 1 , wherein the one or more codeword metrics include a number of bits being flipped during decoding of the code block. 
     
     
       4. The method of  claim 1 , wherein the one or more codeword metrics include whether a code block is retransmitted. 
     
     
       5. The method of  claim 1 , wherein the one or more codeword metrics include a number of iterations of an error correction process being performed during the decoding of a code block. 
     
     
       6. The method of  claim 1 , the one or more channel metrics of a channel indicate a relative channel quality compared to an overall channel quality of all the plurality of channels. 
     
     
       7. The method of  claim 6 , the method further comprising determining an average channel quality of all the plurality of channels based on the one or more codeword metrics of all the plurality of codewords. 
     
     
       8. The method of  claim 7 , the method further comprising:
 aggregating codeword metrics of codewords that are at least partially transmitted via a particular channel; and 
 inferring one or more channel metrics of the particular channel based on the aggregated codeword metrics and the average channel quality of the plurality of channels. 
 
     
     
       9. The method of  claim 1 , further comprising:
 computing a weighted average of codeword metrics of codewords that are at least partially transmitted via a particular channel, wherein a greater weight is given to a codeword metric that is based on codewords received in a more recent time interval. 
 
     
     
       10. The method of  claim 7 , the method further comprising:
 when the relative channel quality of a particular channel is lower than a threshold, determining that interference is present in the particular channel. 
 
     
     
       11. The method of  claim 7 , the method further comprising:
 in response to determining that interference is present, notifying a transmitter that has transmitted the codewords. 
 
     
     
       12. The method of  claim 1 , wherein the one or more channel metrics of each channel are inferred based on codeword metrics of codewords received in a predetermined time window ending at a current time. 
     
     
       13. The method of  claim 1 , wherein the particular error control coding method is one of (1) a low-density parity-check (LDPC) coding method, (2) a turbo coding method, or (3) a convolutional code. 
     
     
       14. A frequency hopping communication system comprising:
 an FEC decoder; and 
 a channel metric processor; wherein: 
 the FEC decoder is configured to:
 decode a plurality of codewords using a particular error control coding method, each of the plurality of codewords comprising portions received from a plurality of channels in the frequency hopping channel system; 
 for each decoded codeword, generate one or more codeword metrics based on cost of correcting errors during decoding of the plurality of codewords; 
 
 the channel metric processor is configured to: 
 infer one or more channel metrics of the plurality of channels based on the one or more codeword metrics of the plurality of codewords; and 
 based on the inferred one or more channel metrics, reduce a reliability metric of a particular channel or cause the FEC decoder to ignore incoming symbols received via a particular channel. 
 
     
     
       15. The frequency hopping communication system of  claim 14 , wherein the one or more codeword metrics include a number of errors corrected during decoding of a code block. 
     
     
       16. The frequency hopping communication system of  claim 14 , wherein the one or more codeword metrics include a number of bits of codewords being flipped during decoding. 
     
     
       17. The frequency hopping communication system of  claim 14 , wherein the one or more codeword metrics include whether a codeword is retransmitted. 
     
     
       18. The frequency hopping communication system of  claim 14 , wherein the one or more codeword metrics include a number of iterations of an error correction process that is performed on a codeword. 
     
     
       19. The frequency hopping communication system of  claim 14 , the channel metric processor further configured to
 compute a weighted average of codeword metrics of codewords that are at least partially transmitted via a particular channel, wherein a greater weight is given to a codeword metric that is based on codewords received in a more recent time interval; and 
 infer one or more channel metrics of the particular channel based on the weighted average of codeword metrics. 
 
     
     
       20. A method for detecting interference in a particular channel of a plurality of frequency hopping channels based on codeword metrics obtained during decoding of codewords, the method comprising:
 receiving a plurality of symbols via the plurality of frequency hopping channels; 
 converting the plurality of symbols into a plurality of codewords; 
 decoding the plurality of codewords based on a particular error control coding method; 
 for each decoded codeword, obtain one or more codeword metrics based on errors corrected during decoding of the codeword; 
 for each particular channel of the plurality of frequency hopping channels,
 inferring one or more channel metrics of the particular channel based on (1) one or more symbol metrics associated with quality of symbols that were transmitted via the particular channel, or (2) the codeword metrics associated with messages that were at least partially transmitted via the particular channel; 
 determining whether interference is present in the particular channel based on the inferred one or more channel metrics; and 
 in response to determining that the interference is present in the particular channel, reducing a frequency of using the particular channel in future communications for a predetermined period.